The present invention relates to a motor rotation detection technique used for automatic operation functions of switching devices, and particularly, to a technique which is effective for applying to a motor rotation detection structure suited for a ripple voltage detection system with a rectified waveform while an armature core is in rotation.
As techniques examined by the present inventor, examples of automatic operation functions of switching device such as power windows for vehicles, or the like include a lock current detection system, a slip ring system or the like. The lock current detection system detects upward current values caused by stopping of the motor. The slip ring system detects repeating pulses by rotating a rotating member in which conductive section and non-conductive sections are alternately arranged. However, the lock current detection system has a limitation to a lock bound current value, and the slip ring system has a problem of increase of number of parts.
In addition to these, there is a ripple voltage detection system for reading signals with a controller connected to the motor and for detecting a ripple voltage of the rectified waveform with this signal rectified. The ripple voltage detection system determines that the motor is locked if the ripple voltage exceeding a certain voltage range is not generated during a certain period, and turns off current flowing the motor.
Now, a conventional motor is able to meet the ripple voltage detection system detecting the rectified waveform. But, since number of slots of the armature core is increased to lower cogging torque, potential difference between commutator segments becomes small and the ripple voltage also is decreased (FIG. 4). This results in detecting no ripple voltage and causing a problem that the automatic operation does not function. In this conventional motor, the number of windings for each slot thereof is same.
In addition, as a winding technique of coil wound around the armature core, for example, techniques recited in Japanese Patent Application Laid-Open Publication Nos. 10-285854 and 8-126239 are mentioned. The technique of the former Publication (No. 10-285854) is one that the coil is wrapped in the number of (N+n) for the beginning and (Nxe2x88x92n) for the ending relative to the predetermined number N of winds in order to prevent becoming fat shape as a result of characteristic modification. The technique of the latter Publication (No. 8-126239) is one that the slot profile in accord with the number of winds is modified in order to modify the characteristics without changing coil shape. Consequently, each technique of the foregoing Publications is unable to apply to the ripple voltage detection system, and is not a technique that takes into account the ripple voltage unlike the present invention.
Accordingly, an objection of the present invention is to provide a motor rotation detection structure that can achieve the automatic operation function by using the ripple voltage detection system with the above-mentioned rectified waveform. That is, by keeping eyes on the number of windings per slot of the armature core that has influence on the ripple voltage, since the ripple voltage is increased by modifying this number of windings, and the cogging torque and the number of parts are brought to be equivalent, the automatic operation function is achieved.
The present invention applies to the motor rotation detection structure comprising an armature core with a plurality of slots, aplurality of coils wound around respective slots, and a commutator with a plurality of segments connected with respective coils. And, the present invention has the following features.
That is, the motor rotation detection structure according to the present invention is characterized in that the structure has a means to detect the ripple voltage. The means is one that the number of windings of respective coils wound around respective slots of armature core is modified per respective slots, and that the potential difference between a segment and other segments adjacent thereto of the commutator is made larger in order to detect the ripple voltage of rectified waveform when the armature core is rotated. This allows the ripple voltage to be increased and the cogging torque to be made equivalent to the number of parts, relative to the automatic operation function in the ripple voltage detection system.
In this configuration, to solve the problem of difficulty to achieve characteristic matching due to the increase of number of slots, the number of winds of respective coils wound around respective slots and the total winds of all coils are subtly adjusted so as to increase the number of slots of the armature core. This results in facilitating the achievement of characteristic matching.